Integrated multipoint fixation screw

ABSTRACT

Bone anchor assemblies and related methods are disclosed herein that can provide for improved fixation of a primary bone anchor. A bone anchor assembly can include a base rotatably received within a rod-receiving member. The base can have a toroid body with a radially-extending portion including at least one auxiliary bone anchor opening that can receive an auxiliary bone anchor to augment fixation of a primary bone anchor of the bone anchor assembly. The base can be rotated relative to the rod-receiving member and the primary bone anchor such that the at least one auxiliary bone anchor opening can be placed in a desired position for supplemental fixation.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/976,766, filed on Feb. 14, 2020, entitled “Integrated MultipointFixation Screw,” which is hereby incorporated by reference in itsentirety.

FIELD

Orthopedic implants and related methods are disclosed herein. Forexample, bone anchor assemblies with multiple bone engagement points aredisclosed.

BACKGROUND

Bone anchor assemblies can be used in orthopedic surgery to fix boneduring healing, fusion, or other processes. In spinal surgery, forexample, bone anchor assemblies can be used to secure a spinal fixationelement to one or more vertebrae to rigidly or dynamically stabilize thespine. Bone anchor assemblies can also be used as an engagement pointfor manipulating bone (e.g., distracting, compressing, or rotating onevertebra with respect to another vertebra, reducing fractures in a longbone, and so forth).

The integrity with which the bone anchor assembly engages the bone canaffect the transfer of corrective biomechanical forces. While a greatamount of care is exercised when placing bone anchor assemblies, it iscommon that a bone anchor assembly will be inserted in a compromisedstate. For example, the bone opening in which the assembly is disposedcan be stripped (e.g., by driving the bone anchor assembly past itsoptimum holding position), the bone anchor assembly can be placedincorrectly (e.g., using an incorrect instrument maneuver such as anover-sized pilot hole), the bone anchor assembly can be placed outsideof its intended trajectory (e.g., within a facet capsule or breachedthrough a pedicle wall), or the bone anchor can be inserted intocompromised bone (e.g., bone that is fractured, osteoporotic, diseased,or otherwise lacking in structural integrity).

When the bone anchor assembly is in a compromised state, there can besub-optimal purchase between the bone anchor assembly and the bone. Thebone anchor assembly may feel unsecure to the surgeon, and it ispossible that the bone anchor assembly could back out or become loosenedover time. There are limited options for the surgeon when faced withthese types of situations. In spinal surgery, for example, the surgeoncan remove the bone anchor assembly and skip the vertebral level, thoughthis can undesirably require expanding the surgical site to additionalvertebral levels. The surgeon can remove and re-insert with a largeranchor, though this may not be an option when space for anchoring in thebone is limited. The surgeon can leave the compromised bone anchorassembly in place, which may be the safest alternative if the boneanchor assembly is in a safe location and attachment to the plate, rod,or other implant construct is definitive, as the additional compromisedfixation may be better than removal.

Even when a bone anchor assembly is placed in a non-compromised state,the geometry of traditional bone anchor assemblies can limit theflexibility with which the bone attachment point can be located withrespect to a plate, rod, or other implant construct coupled to the boneanchor assembly.

There is a continual need for improved bone anchor assemblies andrelated methods.

SUMMARY

Bone anchor assemblies are disclosed herein that can provide forimproved fixation as compared with traditional bone anchor assemblies.An embodiment of an assembly can include a multipoint eyelet componentthat is part of a bone anchor base. The eyelet component can beintegrated into a receiver member assembly in a manner that allowspositioning the eyelet at any desired position around a circumference ofthe receiver member. The eyelet component can accommodate one or moreauxiliary bone anchors that augment the fixation of the assembly'sprimary bone anchor. Surgical methods using the bone anchor assembliesdescribed herein are also disclosed.

In one aspect, a bone anchor assembly can include a base, a receivermember, and a shank. The base can include a toroid body portion and aradial protrusion (e.g., an eyelet or wing) extending radially from thetoroid, the radial protrusion having at least one auxiliary bone anchoropening configured to receive an auxiliary bone anchor. The receivermember can have a proximal end, a distal end, a lumen extending from theproximal end to the distal end, and a rod-receiving recess. The shankcan have a head portion retained within the toroid body of the base anda bone engaging portion that extends distally from the base. The basecan be coupled to the receiver member such that the base is configuredto rotate relative to the receiver member.

The devices and methods described herein can have a number of additionalfeatures and/or variations, all of which are within the scope of thepresent disclosure. In some embodiments, for example, the toroid body ofthe base can extend distally from the receiver member. The base caninclude an extension that can extend proximally from the toroid body.The extension can be received within a lumen of the receiver member. Insome such embodiments, the extension can have a first connection featureand the receiver member can have a second connection feature. The firstconnection feature can be configured to engage with the secondconnection feature such that the base can be rotatably received withinthe receiver member. Further, in some embodiments, the first connectionfeature and the second connection feature can be configured such thatrelative axial movement between the base and the receiver member can berestricted when the first connection feature engages with the secondconnection feature. In some embodiments, the first connection featurecan be a lip at a proximal end of the extension, and the secondconnection feature can be a groove in an inner surface of the receivermember. The groove of the receiver member can be distal to therod-receiving recess.

In some embodiments the bone anchor assembly can include a saddledisposed within the receiver member. The saddle can have a distal-facingsurface that can contact a proximal-facing surface of the extension ofthe base when the base is disposed within the receiver member. In someembodiments, the at least one auxiliary bone anchor opening of theradially-extending portion can include a plurality of auxiliary boneanchor openings. A central lumen of the at least one auxiliary boneanchor opening can extend at a transverse angle relative to a centralaxis of the receiver member. The central lumen of the at least oneauxiliary bone anchor opening can be angled in one of a caudal and acephalad direction. In some embodiments, the central lumen of the atleast one auxiliary bone anchor opening can be angled in one of a medialand a lateral direction.

In another aspect, a surgical method can include driving a shank portionof a bone anchor into a bone of a patient and rotating a base of a boneanchor assembly relative to a receiver member of the bone anchorassembly, the base having a radially protruding portion with at leastone auxiliary bone anchor opening extending therethrough and thereceiver member configured to receive a spinal fixation element. Themethod can include positioning the radially protruding portion of thebone anchor at a desired position relative to the shank portion anddriving at least one auxiliary bone anchor through the at least oneauxiliary bone anchor opening and into bone of the patient.

In some embodiments, driving the at least one auxiliary bone anchorthrough the at least one auxiliary bone anchor opening and into bone ofthe patient can include driving the at least one auxiliary bone anchorthrough the at least one auxiliary bone anchor opening with an insertiontrajectory that can be biased relative to at least one of a central axisof the receiver member and the shank to supplement fixation of the boneanchor within the bone. Rotating the base of the bone anchor assemblycan include rotating the base about a central longitudinal axis of thereceiver member.

In some embodiments the method can include placing a spinal rod withinthe receiver member and securing the spinal rod within the receivermember before driving the at least one auxiliary bone anchor into bone.In other embodiments, placing a spinal rod within the receiver memberand securing the spinal rod within the receiver member can occur afterdriving the at least one auxiliary bone anchor into bone.

The method can further include assembling the bone anchor by couplingthe base to the receiver member such that the base is rotatable withrespect to a central longitudinal axis of the receiver member andinserting the shank through the receiver member and the base such that adistal bone-engaging portion of the shank extends distally from the baseand a head portion of the shank is received within the base. In someembodiments, the shank can be polyaxially rotatable relative to thebase.

Any of the features or variations described above can be applied to anyparticular aspect or embodiment of the present disclosure in a number ofdifferent combinations. The absence of explicit recitation of anyparticular combination is due solely to the avoidance of repetition inthis summary.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects and embodiments of the present disclosure described abovewill be more fully understood from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is an exploded perspective view of one embodiment of a boneanchor assembly of the present disclosure;

FIG. 2 illustrates an exploded perspective view of another embodiment ofa bone anchor assembly of the present disclosure;

FIG. 3 is a cross-sectional view of the bone anchor assembly of FIG. 2;

FIG. 4 schematically illustrates a top view of the base of the boneanchor assembly of FIG. 2 in a first position relative to a receiver ofthe bone anchor assembly of FIG. 2; and

FIG. 5 schematically illustrates a top view of the base of the boneanchor assembly of FIG. 2 rotated to a second position relative to thereceiver of the bone anchor assembly of FIG. 2.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices, systems, and methods disclosedherein. One or more of these embodiments are illustrated in theaccompanying drawings. The devices, systems, and methods specificallydescribed herein and illustrated in the accompanying drawings arenon-limiting embodiments. The features illustrated or described inconnection with one embodiment may be combined with the features ofother embodiments. Such modifications and variations are intended to beincluded within the scope of the present disclosure.

Bone anchor assemblies are disclosed herein that can provide forimproved fixation as compared with traditional bone anchor assemblies. Abone anchor assembly of the present disclosure can include a primaryscrew shank to engage with bone, a base having a radially-extendingprotrusion (e.g., a protruding eyelet, wing, etc.) with at least oneauxiliary bone anchor opening to receive an auxiliary bone anchor, and areceiver member for receiving a spinal fixation element. The base cancouple with the receiver member such that the base can rotate relativeto, and independently of, the receiver member and primary shank. In thismanner, the base can be rotated to adjust the positioning of the one ormore auxiliary bone anchor openings relative to the receiver member andbone anchor once the primary screw shank has engaged with bone, e.g., avertebra, of a patient.

The bone anchor assembly can be assembled by inserting the screw shankinto the base such that a proximal head of the screw shank can be seatedor otherwise retained within the base with a distal bone-engagingportion of the screw shank extending distally from the base. The basecan be inserted into the receiver member and coupled therewith such thatthe base can rotate relative to the receiver. The screw shank can bedriven into patient anatomy, e.g., a vertebra, and the base can berotated freely about a longitudinal axis of the receiver member toposition one or more auxiliary bone anchor openings on a protrusion(e.g., an eyelet, wing, etc.) of the base at a desired location forsupplemental fixation, i.e., fixation beyond that provided by theprimary screw shank. One or more auxiliary bone anchors, also referredto herein as supplemental fixation screws, can be inserted into theauxiliary bone anchor openings and driven to engage with patient anatomyto provide the desired supplemental fixation. A spinal fixation rod canbe placed and/or secured within the receiver member either before orafter placement of the supplemental fixation screws. Accordingly, boneanchor assemblies of the present disclosure can provide supplementalfixation to a primary screw in a strategic and patient-specific manner,without requiring additional components beyond the bone anchor assembly.

FIG. 1 illustrates an exploded view of one embodiment of a bone anchorassembly 100 in accordance with the present disclosure. As noted above,a bone anchor can sometimes be inserted in a compromised state. This canbe undesirable, especially in instances in which there is limited bonearea in which to install additional bone anchors. The illustrated boneanchor assembly 100 can allow for supplemental fixation of a primarybone anchor in a compact footprint, without necessarily requiringremoval or re-insertion of the primary bone anchor. As shown, the boneanchor 100 can include a primary bone anchor 102, also referred to as aprimary screw shank, a base 104, a receiver member 106 for receiving aspinal fixation element (not shown), such as a spinal rod, to be coupledto the bone anchor, and one or more auxiliary bone anchors 108. Aclosure mechanism (not shown), such as a set screw, can capture a spinalfixation element within the receiver member 106 and fix the spinalfixation element with respect to the receiver member. The spinalfixation element, e.g., the spinal rod, can either directly contact thereceiver member 106 (or other component such as base 104 and/or boneanchor 102, or can contact an intermediate element, e.g., a saddle 105,as shown, for example, in FIGS. 2 and 3. In use, the base 104 can becoupled to the receiver member 106 such that the base can rotaterelative to the receiver member about a central longitudinal axis A1 ofthe receiver member, while relative movement along the longitudinal axisA1 can be restricted or limited. One or more supplemental fixationscrews 108 can be driven into bone through a corresponding one or moreauxiliary bone anchor openings 124 of the base 104 and can supplementfixation of the bone anchor 102 within patient anatomy.

The primary screw shank 102 can include a distal threaded shaft 110configured to engage bone and a proximal head 112. The proximal head 112can generally have the shape of a truncated sphere with a planarproximal surface and an approximately spherically-shaped distal surface.The proximal head 112 of the screw shank 102 can engage with a distalend of the base 104, for example, in a ball and socket like arrangementin which the proximal head 112 can pivot relative to the base 104. Adistal surface of the proximal head 112 of the shank 102 and a matingsurface within the distal end of the base 104 can have any shape thatcan facilitate this arrangement, including, for example, spherical,toroidal, conical, frustoconical, and any combination thereof.

The distal shaft 110 of the shank 102 can be configured to engage boneand, in the illustrated embodiment, can include an external boneengaging thread. The thread form for the distal shaft 110, including thenumber of threads, the pitch, the major and minor diameters, and thethread shape, can be selected to facilitate connection with bone.Exemplary thread forms are disclosed in U.S. Patent ApplicationPublication No. 2011/0288599, filed on May 18, 2011, and in U.S. PatentApplication Publication No. 2013/0053901, filed on Aug. 22, 2012, bothof which are hereby incorporated by reference herein.

The base 104 can have a toroid body portion 114 with a radiallyprotruding portion (e.g., an eyelet or wing) 116 extending radiallytherefrom. An extension 118 can extend proximally from the toroid body114. The proximal extension 118 can include a lip 120, or otherconnection feature, such as, for example, one or more prongs, a groove,etc., for engagement with a complimentary connection feature of thereceiver 106. In some embodiments the extension 118 and the lip 120 canbe deformable. For example, the lip 120 can compress radially inwardwhen the lip 120 is received within a lumen 136 of the receiver member106, and can expand radially outward from a compressed position when thelip 120 aligns with a groove 142 of the receiver member. In this manner,the lip 120 of the base 104 can engage with the groove 142 of thereceiver member 106 to retain the base 104 within the receiver member106. In some embodiments the lip 120 and the extension 118 can be adeformable monolithic structure. In other embodiments, a connectionfeature, e.g., the lip 120, can be formed on or extend from the toroidbody 114 itself, and the proximal extension 118 can be omitted.

A lumen 122 with a central longitudinal axis A1 can extend through thebase 104, and, more particularly, can extend through the toroid body 114and the proximal extension 118 (the central longitudinal axis A1 of thelumen 122 may also be referred to as the central longitudinal axis A1 ofthe base 104). The screw shank 102 can be inserted through the lumen 122such that the distal threaded portion 110 extends distally from thetoroid body 114 while the head portion 112 of the screw shank 102 can bereceived within the toroid body 114. In some embodiments, an interiorsurface of the toroid body 114 can include features complementary to theproximal head 112 of the screw shank 102 such that the screw shank canbe retained within the toroid body 114 and, in some embodiments, canmove polyaxially relative to the toroid body. While a “top-down”assembly is described above, wherein the screw shank 102 is passeddistally through the base 104 until the proximal head 112 is receivedwithin the toroid body 114 of the base, in other embodiments theassembly can be configured for “bottom loading,” wherein the screw shank102 is passed proximally through the base 104 in order to seat theproximal head 112 into the toroid body 114. This can be accomplished,for example, by forming the toroid body 114 and/or proximal head 112such that it can deform to allow passage of the proximal head into arecess of the toroid body. Examples of features permitting such couplingcan include the use of elastically deformable materials, elastic fingersforming a collet or other gripping structure, etc.

The protruding portion or wing 116 can extend from the toroid body 114and can form part of the base 104. The protruding portion 116 can extendradially outward from the toroid body 114, i.e., away from the centrallongitudinal axis A1 of the lumen 122. An auxiliary bone anchor opening124 can be formed in the wing 116. While a single opening 124 is shownextending through the wing 116 of FIG. 1, in some embodiments, the wing116 can include a plurality of auxiliary bone anchor openings 124. Theauxiliary bone anchor opening 124 can be configured to receive anauxiliary fixation element 108. As shown in FIG. 1, a centrallongitudinal axis A2 of the opening 124 can extend substantiallyparallel to the central longitudinal axis A1 of the lumen 122. In otherembodiments, the opening 124 can extend with a biased or angledtrajectory relative to the central axis A1 of the lumen 122. Forexample, the central axis A2 of the opening 124 can extend at an obliqueangle relative to the central longitudinal axis A1 of the lumen 122. Inthis manner, an auxiliary bone anchor 108 can be received through theauxiliary bone anchor opening 124 and can be placed within patientanatomy with a caudal or cephalad trajectory, depending on placement ofthe protruding portion 116 relative to the patient anatomy.Additionally, or alternatively, the central axis A2 of the opening 126can extend radially inward towards the central axis A1 of the opening122 or radially outward away from the central axis A1 of the opening122. In embodiments with a plurality of auxiliary bone anchor openings124 in the protruding portion 116, each opening 124 can be angled orbiased to have either the same or different trajectories. Furtherfeatures and embodiments of an auxiliary bone anchor opening can befound in U.S. patent application Ser. No. 16/583,233, filed on Sep. 25,2019, entitled “Multipoint Angled Fixation Implants for Multiple Screwsand Related Methods,” the entire contents of which are herebyincorporated by reference.

In some embodiments, each auxiliary bone anchor opening 124 can includeany of a number of features for accepting an auxiliary bone anchor 108at varying angles, such as, for example, conical, spherical, orparabolic threads. For example, as discussed in U.S. patent applicationSer. No. 16/583,233 with respect to, for example, FIGS. 2A-2M, theopening 124 can be at least partially threaded to receive avariable-angle locking screw 108 having a threaded proximal head 132. Asshown in FIG. 1, the opening 124 can have a plurality of columns ofthreads 128 spaced apart to define a plurality of non-threaded recesses130. In this manner, the threads of the opening 124 can form aninterlocking interface and mate with threads 125 of the supplementalfixation screw 108 to lock the screw 108 therein. In one embodiment, thethreads of the opening 124 can be conical threads. The columns ofthreads 128 can be arranged around an inner surface of the opening 124for engaging threads 132 on a head of a locking and/or a variable-angleauxiliary bone screw 108. The supplemental fixation screw 108 can thusbe locked within the protruding portion 116, and specifically within theopening 124, co-axially with the central axis A1 of the base 104 or at aselected angle within a range of selectable angles relative to thecentral axis of the base. For example, the screw 108 can be insertedinto the opening 124 along a trajectory A3 that can extend at atransverse angle relative to the central axis A2 of the opening. Theopening 124 can have any number of columns of threads 128 (e.g., two,three, four, etc.) to facilitate variable angle locking with thesupplemental fixation screw 108. Additionally, or alternatively, theopening 124 can include one or more additional locking components, suchas a cam, and/or can facilitate locking with the screw 108 throughmaterial deformation, e.g., splaying of the auxiliary bone anchoropening.

The auxiliary bone anchor 108 can include features to facilitate thisvariable-angle locking, such as a proximal head that is at leastpartially spherical having a thread with a profile that follows thearc-shaped radius of curvature of the spherical portion of the head. Thevariable-angle capability of the interlocking interface (i.e., thescrew/opening interface) can allow the user to place a locking auxiliarybone anchor into the bone at any angle defined within angulation limits,thus providing improved placement flexibility and eliminating orreducing the need to conform the wing 116 to a bone surface to achieve adesired insertion angle. Accordingly, the auxiliary bone anchor 108 canbe driven into the bone with a diverging or converging longitudinal axisrelative to the primary bone anchor 102. In instances in which aplurality of bone anchors 108 can each be driven through an opening ofthe protruding portion 116, the bone anchors 108 can be driven into thebone with diverging or converging longitudinal axes relative to eachother and/or relative to the primary bone anchor 102. Biased or angledtrajectories of the auxiliary bone anchors 108 can provide improvedresistance to pullout. A locking interface between an auxiliary boneanchor opening and an auxiliary bone anchor can increase stability andprevent the auxiliary bone anchor from backing out of the opening.

As described above, the auxiliary bone anchor opening 124 can include alocking interface with one or more locking features to lock a head ofthe auxiliary bone anchor within the opening 124. In other embodiments,the opening 124 can have a lagging interface with the auxiliary boneanchor, in which the head of the auxiliary bone anchor does notindependently lock relative to the opening 124. In some suchembodiments, the interior surface of the opening 124 can be smooth orspherical, without threads or locking features.

The receiver member 106 can have a proximal end 106 p, a distal end 106d, and a lumen 136 extending therebetween. The proximal end 106 p canhave a pair of spaced apart arms 138A, 138B defining a U-shapedrod-receiving recess 140 therebetween for receiving a spinal fixationelement, e.g., a spinal rod. Each of the arms 138A, 138B can extend fromthe distal end 106 d of the receiver member 106 to a free end. The outersurfaces of each of the arms 138A, 138B can include a feature, such as arecess, dimple, notch, projection, or the like, to facilitate connectionof the receiver member 106 to instruments. For example, the outersurface of each arm 138A, 138B can include an arcuate groove at therespective free end of the arms. Such grooves are described in moredetail in U.S. Pat. No. 7,179,261, issued on Feb. 20, 2007, which ishereby incorporated by reference herein. A closure mechanism, such as aset screw, (not shown) can be positioned between and can engage the arms138A, 138B to capture a spinal fixation element, e.g., a spinal rod,(not shown) within the receiver member 106 and fix the spinal fixationelement with respect to the receiver member. For example, the arms 138A,138B can have internal threads 141 that can engage with external threadsof the closure mechanism.

The distal end 106 d of the receiver member 106 can have a distal endsurface which is generally annular in shape defining an opening throughwhich at least a portion of the base 104 and the shank 102 can extend.For example, the extension 118 of the base 104 can be inserted throughthe distal opening of the receiver member 106 such that the lip 120 ofthe extension can engage with the groove 142 of the receiver member andthe toroid body 114 of the base can extend distally from the receivermember. As described in detail with reference to FIGS. 2-4, the base 104can couple with the receiver member 106 such that the base can berotated relative to the receiver member about a central longitudinalaxis of the receiver member.

In the assembled configuration of the bone anchor assembly 100, acentral longitudinal axis of the lumen 136 of the receiver member 106can be co-axial with the central longitudinal axis A1 of the lumen 122of the base. The base 104 can couple with the receiver member 106 suchthat the base 104 can rotate about the central axis A1 relative to thereceiver member. In some embodiments, the base 104 can rotate 360degrees about the central axis A1 relative to the receiver member inboth a clockwise or counter-clockwise direction. Relative axial movementalong the central axis A1 between the base 104 and the receiver member106, however, can be limited or restricted. The receiver member 106 canreceive a spinal fixation element, such as a spinal rod (not shown),within the rod-receiving recess 140 such that the spinal fixationelement can extend transverse relative to the longitudinal axis A1.

The structure, assembly, and use of bone anchor assemblies of thepresent disclosure will now be described in greater detail withreference to the alternative embodiment of a bone anchor assembly 100′as shown in FIGS. 2 and 3. FIG. 2 shows an exploded perspective view ofthe bone anchor assembly 100′, and FIG. 3 shows a cross-sectional viewof the assembled bone anchor of FIG. 2. Except as described herein or aswill be readily appreciated from the present disclosure, the bone anchorassembly 100′ can be substantially similar to the bone anchor assembly100 described above, with like-numbered components generally havingsimilar features. In use, the base 104′ can be received within thereceiver member 106′ such that the toroid body 114′ can extend distallyfrom the receiver member and the base can rotate relative to thereceiver. Optionally, a saddle 105 can be interposed between the base104′ and a spinal fixation element (not shown) received within thereceiver member 106′. The head 112 of the shank 102 can be receivedwithin the base 104′, while the distal shaft 110 of the shank can extenddistally from the base and, accordingly, from the receiver member 106′,to engage with bone. The protruding portion 114′ can be rotated relativeto the receiver 106′ and can be positioned such that the one or moreauxiliary bone anchor openings 124′ can be strategically locatedrelative to the shank 102 and patient anatomy to provide the desiredsupplemental fixation. One or more auxiliary bone anchors can be driventhrough the one or more auxiliary bone anchor openings in the protrudingportion of the base to engage with bone and provide supplementalfixation support to that of the primary bone anchor.

The lip 120′ of the base 104′ can be received within the groove 142′ ofthe receiver member 106′ such that the base 104′ can rotate relative tothe receiver member 106′ about the axis A1. Relative axial movement,i.e., movement along the axis A1, however, can be restricted, forexample, by tolerance dimensions of the groove 142′ relative to the lip120′ and/or a length of the extension 118′ of the base 104′ along thedirection of the axis A1. In some embodiments, the extension 118′ andthe lip 120′ can include one or more deformable fingers 121 with gaps123 therebetween. The fingers 121 can compress radially inward whenreceived within the lumen 136′ of the receiver member 106′, and canexpand outward when the lip 120′ aligns with the groove 142′ of thereceiver member. While the embodiments illustrated in FIGS. 1-3 show aconnection feature of the base 104, 104′ as the lip 120, 120′ and acomplementary connection feature of the receiver member 106, 106′ as thegroove 142, 142′ alternative complementary connection features can beused and are within the scope of the present disclosure, so long as theconnection between the base and the receiver member allows for relativerotation therebetween. By way of non-limiting example, a groove or oneor more prongs can be formed on an interior distal surface of thereceiver member 106 and can engage with a groove formed on an externalsurface of the extension 118.

FIG. 3 shows the base 104′ and the saddle 105 received within thereceiver member 106′. At least a portion of the extension 118′ of thebase 104′ can be received within a distal portion of the lumen 136′ ofthe receiver member 106′ such that the toroid body 114′ of the baseextends distally from the distal surface of the receiver member. Asdiscussed above, the lip 120′ of the extension 118′ can be deformable,and can compress radially inward during insertion of the extension intothe receiver member 106′. The lip 120′ can then expand to its initialstate when the lip aligns with the groove 142′ of the receiver member106′, as shown in FIG. 3, and can retain the base 104′ within thereceiver member. A proximal facing surface of the toroid body 114′ cancontact a distal-facing surface of the receiver member 106′. In otherembodiments, a portion of the extension 118′ can extend distally fromthe receiver member 106′ such that the toroid body 114′ does not contactthe receiver member 106′. As described above, the wing 116′ can extendfrom the toroid body 114′ radially outward from the central axis A1,i.e., radially outward relative to the lumen 122 of the base 104′. Inthe assembled configuration, the wing 116′, having at least oneauxiliary bone anchor opening 124, can rotate with the base 104′relative to the receiver member 106′.

The saddle 105 can be received within the lumen 136′ of the receivermember 106′, with at least a portion of the saddle in contact with thebase 104′. The saddle 105 can have a proximal portion 105 p, a distalportion 105 d, and a lumen 107 extending therebetween. The saddle 105can include a pair of spaced apart arms 109A, 109B defining a U-shapedseat 111 that can receive the spinal fixation element, and adistal-facing surface 113 of the proximal portion 105 p that can abut aproximal-facing surface of the base 104′ and/or a portion of theproximal head 112 of the screw shank 102. The distal portion 105 d ofthe saddle 105 can be received within the extension 118′ of the base104′ such that the distal portion of the saddle can extend into thelumen 122 of the base. The saddle 105 can be positioned within thereceiver member 106′ and interposed between the base 104 and a spinalfixation element in the rod-receiving recess 140. For example, thesaddle 105 can be inserted into the lumen 136 of the receiver member 106such that the arms 109A, 109B deflect radially inward. As the saddle 105advances to a position where a distal portion of the arms 109A, 109Balign with a groove 143 formed in the receiver member 106, the arms canexpand radially outward to seat portions thereof within the groove 143,thereby retaining the saddle to the receiver member. Dimensions of thegroove 143 and portions of the arms 109A, 109B configured to be receivedtherein can be set to allow for desired axial movement of the saddle 105relative to the receiver member 106 when, e.g., varying forces exertedby the saddle on the shank 102. More particularly, with the proximalhead 112 of the shank 102 received within the base 104′, the saddle 105can compress a distal outer surface of the head of the shank 102 intodirect, fixed engagement with a distal inner surface 119 of the base104′. The head 112 of the shank 102 can be received and retained withinthe base 104′, i.e., within the lumen 122′, while the distal shaft 110of the shank can extend distally from the toroid body 114′ of the base104′. The shank 102 can be inserted into the base 104′ before or afterinserting the base 104′ into the receiver member 106′.

In the assembled configuration, the base 104′ can rotate 360 degreesrelative to the receiver 106′. For example, FIG. 4 shows a top view of afirst position of the base 104′ with respect to the receiver member106′, in which the wing 116′ can extend to the left of the receiver,with respect to the illustrated view in FIG. 4, at substantially amid-line of the receiver arm 138A′. The base 104′ can be rotatedrelative to the receiver 106′ in either a clockwise or counter-clockwisedirection, indicated by arrows 202 and 204, respectively. For example, auser can grasp the wing 116′ or toroid body 114′ and rotate the base104′ clockwise to place the wing 116′ in a second position, for examplethe position shown in FIG. 5, that is different from the first position.

One embodiment of a method of use of the bone anchor assembly 100 willnow be described. The bone anchor assembly 100 can be assembled prior toimplantation into a patient. The screw shank 102 can be top-loaded intothe base 104. More particularly, the screw shank 102 can be passeddistally through the lumen 122 of the base 104 such that the shaft 110of the screw shank can extend distally from the toroid body 114 of thebase while the proximal head 112 of the screw shank can be receivedwithin the lumen 122 of the base 104. Alternatively, in someembodiments, the screw shank 102 can be bottom-loaded into the base 104.

The base 104 with the shank 102 received therein can be inserted intothe receiver 106 such that the base can be rotated relative to thereceiver. More particularly, the extension 118 can be inserted throughthe distal opening of the receiver 106 and can be moved proximallywithin the lumen 136 of the receiver until the lip 120 of the base 104can be captured, e.g., within the groove 142 of the receiver 106.Alternatively, the base 104 can be coupled to the receiver 106 prior toinserting the shank 102 through the base 104. In such instances, theshank 102 can be moved distally through the lumen 136 of the receiver106 and the lumen 122 of the base 104. In some embodiments, the base 104and the receiver member 106 can be manufactured as a single componentwith the base rotatable relative to the receiver member 106 as describedherein. As discussed above, with the base 104 connected with thereceiver 106, the base, including the toroid body 114 and the wing 116,can rotate relative to, and independently of, the receiver 104 about thecentral axis A1.

With the receiver member 106, the base 104, and the screw shank 102,i.e., the primary bone anchor, assembled, the shank can be driven intobone in accordance with standard surgical technique. For example, thebone anchor assembly 100 can be a polyaxial bone screw designed forposterior implantation in the pedicle or lateral mass of a vertebra.With the shank 102 implanted into bone, the wing 116 of the base 104 canbe rotated relative to the shank 102 and the receiver 106 to positionthe one or more auxiliary bone anchor openings 124 at a desiredlocation. Various factors can be taken into consideration whenpositioning the wing 116 and auxiliary bone anchor openings 124including, for example, placement of the shank 102, patient anatomy,other instrumentation, and surgical procedure requirements, such as,whether the bone into which the shank 102 engages is to be fused to oneor more adjacent vertebrae.

One or more auxiliary bone anchors 108 can then be driven through theone or more corresponding auxiliary bone anchor openings 124 of the wing116 into bone to supplement fixation of the bone anchor 100. Asdiscussed in detail above, one or more of the auxiliary bone anchors 108can be driven with an angled or biased trajectory relative to thecentral axis A1 of the bone anchor, the shank 102, and/or one or moreother auxiliary bone anchor. A spinal rod can be placed within therod-receiving recess 140 of the receiver member 106 and can be securedwithin the receiver member with a closure, for example, a set screw. Theone or more auxiliary bone anchors 108 can be placed either before orafter placement and/or securing of the spinal rod within the receivermember.

In any of the above embodiments or methods, the primary bone anchor canbe omitted and the user can rely solely on the one or more auxiliaryfixation features to secure the bone anchor. This can advantageouslyallow the position of the fixation to be completely offset from thereceiver member, for example if an initially placed bone anchor needs tobe removed due to improper positioning or inadequate purchase, or whenthe receiver member needs to be positioned over a location where a boneanchor cannot be inserted.

While the methods illustrated and described herein involve a bone anchorplaced in the pedicle or lateral mass of vertebral bone, it will beappreciated that the systems and methods herein can be used in any bone,in non-bone tissue, or in non-living or non-tissue objects.

The auxiliary fixation members disclosed herein can be implanted in thesame surgical procedure as the bone anchor, receiver member, and spinalrod, or, in the case of revision surgery, during a subsequent surgicalprocedure.

It should be noted that any ordering of method steps expressed orimplied in the description above or in the accompanying drawings is notto be construed as limiting the disclosed methods to performing thesteps in that order. Rather, the various steps of each of the methodsdisclosed herein can be performed in any of a variety of sequences. Inaddition, as the described methods are merely exemplary embodiments,various other methods that include additional steps or include fewersteps are also within the scope of the present disclosure.

As evident from the foregoing, in at least some embodiments, the systemsand methods disclosed herein can provide enhanced fixation for a givensurgical site, providing greater bone fixation strength at a givenlocation without necessarily requiring moving the fixation to anadditional vertebra or skipping/increasing the involved vertebrallevels.

The bone anchor assemblies disclosed herein and the various componentparts thereof can be constructed from any of a variety of knownmaterials. Exemplary materials include those which are suitable for usein surgical applications, including metals such as stainless steel,titanium, or alloys thereof, polymers such as PEEK, ceramics, carbonfiber, and so forth. The various components of the devices disclosedherein can be rigid or flexible. One or more components or portions ofthe device can be formed from a radiopaque material to facilitatevisualization under fluoroscopy and other imaging techniques, or from aradiolucent material so as not to interfere with visualization of otherstructures. Exemplary radiolucent materials include carbon fiber andhigh-strength polymers.

The method and devices described above relate to a spinal surgicalapplication. While this is one contemplated use, the methods and devicesof the present disclosure can be equally adapted for use in other areasof a patient's body, and can be used with any human or animal implant,in any of a variety of surgeries performed on humans or animals, and/orin fields unrelated to implants or surgery. As such, the devicesdescribed herein can be formed in a variety of sizes and materialsappropriate for use in various areas of a patient's body. The systemsand methods disclosed herein can be used in minimally-invasive surgeryand/or open surgery.

Although specific embodiments are described above, it should beunderstood that numerous changes may be made within the spirit and scopeof the concepts described. Accordingly, it is intended that thisdisclosure not be limited to the described embodiments, but that it havethe full scope defined by the language of the following claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

What is claimed is:
 1. A bone anchor assembly, comprising: a base havinga toroid body portion and a radially-extending portion including atleast one auxiliary bone anchor opening configured to receive anauxiliary bone anchor, the base comprising an extension extendingproximally from the toroid body portion; a receiver member having aproximal end, a distal end, with a lumen extending therebetween, and arod-receiving recess; and a shank having a head portion retained withinthe toroid body portion and a bone engaging portion that extendsdistally from the base; wherein the base is coupled to the receivermember such that the base is configured to rotate relative to thereceiver member, and wherein the extension is received within the lumenof the receiver member.
 2. The bone anchor of claim 1, wherein thetoroid body portion of the base extends distally from the receivermember.
 3. The bone anchor of claim 1, wherein the extension of the basehas a first connection feature and the receiver member has a secondconnection feature, wherein the first connection feature is configuredto engage the second connection feature such that the base is rotatablyreceived within the receiver member.
 4. The bone anchor of claim 3,wherein the first connection feature and the second connection featureare configured such that relative axial movement between the base andthe receiver member is restricted when the first connection featureengages with the second connection feature.
 5. The bone anchor of claim3, wherein the first connection feature is a lip at a proximal end ofthe extension and the second connection feature is a groove in an innersurface of the receiver member.
 6. The bone anchor of claim 5, whereinthe groove of the receiver member is distal to the rod-receiving recess.7. The bone anchor of claim 3, wherein the first connection featurecomprises a substantially continuous sidewall that is configured toengage the second connection feature.
 8. The bone anchor of claim 1,further comprising a saddle disposed within the receiver member, thesaddle having a distal-facing surface configured to contact aproximal-facing surface of the extension disposed within the receivermember.
 9. A surgical method, comprising: driving a shank of a boneanchor into a bone of a patient; rotating a base of the bone anchorrelative to a receiver member of the bone anchor, the base having aradially-extending portion with at least one auxiliary bone anchoropening extending therethrough and an extension extending proximallytherefrom, the receiver member configured to receive a spinal fixationelement; disposing the extension within the receiver member; positioningthe radially-extending portion of the base at a desired positionrelative to the shank; and driving at least one auxiliary bone anchorthrough the at least one auxiliary bone anchor opening in theradially-extending portion and into bone of the patient.
 10. The methodof claim 9, wherein rotating the base of the bone anchor furthercomprises rotating the base about a central longitudinal axis of thereceiver member.
 11. The method of claim 9, further comprising placing aspinal rod within the receiver member and securing the spinal rod withinthe receiver member before driving the at least one auxiliary boneanchor into bone.
 12. The method of claim 9, further comprising placinga spinal rod within the receiver member and securing the spinal rodwithin the receiver member after driving the at least one auxiliary boneanchor into bone.
 13. The method of claim 9, further comprisingassembling the bone anchor by: coupling the base to the receiver membersuch that the base is rotatable about a central longitudinal axis of thereceiver member; and inserting the shank through the receiver member andthe base such that a distal bone-engaging portion of the shank extendsdistally from the base and a head portion of the shank is receivedwithin the base.
 14. The method of claim 13, wherein the shank isrotatable polyaxially relative to the base.
 15. The method of claim 9,wherein the base is rotated relative to the receiver member and theshank without translating relative to the shank.